Method of heat treating metal parts



July 21, 1931- R. v. wlLsoN v 1,815,691

.METHOD-,OF l'EA'ZI TREATING METAL PARTS Y Filed oct. s1, 1928 PatentedJuly 2l, 1931 ROGER WILSON, 0F LA GRANGE,

COMPANY, INCORPORATED, OF NEW ILLINOIS, ASSIGNOR T0 WESTERN ELECTRICYORK, N. Y., A. CORPORATION OF NEW YORK METHOD OF. HEAT TREATIN G METALPARTS Application mea oetoberei, 192s. serial No.l 316,149.

This invention relates to a methodof heat treating metal parts and moreparticularly to the bright annealingl of iron parts.

In the heat treating of iron articles, it has lbeen customary to storethe articles in a sealed container, place the -container in a heatingchamber and gradually raise the temperature to the desired maximum,after which the container is withdrawn from the furnace and placed undera cooling hood `Wherein the cooling of the container and contents iseffected slowly. Before placing in the furnace, the container issealedwith a material designed to permit escape of oxygen therefrom as thetemperature is raised and the air therewithin expands, and whichmaterial will harden and prevent vingress of oxygen to the interior duetov atmospheric pressure when the temperature issubsequently lowered. Alarge percentage of the oxygen contained in the container is ejected inthis manner, but in some'cases a sufcient quantity of the ox gen remainswithin the container during t e entire process to oxidize the iron partssomewhat and thus discolor them.

The object of the present invention is to provide a simple andinexpensive method 'for heat treating parts wherein predeterminedatmospheric conditions are' insured throughout the process.

According to the features of the'invention, a quantity'ofmaterialoxidizableat a considerably lower temperature thanthe parts andhaving a relatively large area, such as copper tinsel, is placedadjacent to'but not in direct contact with the parts in an annealingcontainer. y

A material having a higher ailinity for oxygen at high temperatures,such as magnesium powder, maybe added with the copper tinsel to insurethat the atmosphere Within the container shall be free of oxygenthroughout the annealingprocess,l and to reduce the .articles within thecontainer to the extent in which they may have previously becomeoxidized.

It is believed that the invention will be more clearly understoodby'reference to the accompanying drawing in which the figure representsa vertical section of a loaded annealing container-prepared for heating.

In the drawing an annealing container generally denoted by the numeral10, comprises'vertical side walls 11, the up er portion of whichconsists of an upwardly rojecting lip 12 and an inner portion 13.uitably arranged within the container are a desired number of-articlessuch as iron parts,

generallydenoted by the numeral 14. Rest ing upon the inner portions 13is a tray 15 upon which is placed a quantity of a material which byreason of its large surface area as compared to its weight is capable ofabsorbing a large portion of the oxygen remaining in the container afterthe oxygen content is materially reduced by heat expansion, and alsosuch oxygen as may be drawn into the container during the coolingprocess. On the tray is placed also a quantity of material such asmagnesium, aluminum or 'other of the metals comprising the class whichare capablel of combining vigorously with oxygen at the higher of thetemperatures Within the range reached during the heat treating process.The drawing illustrates the use respec# tively of a desired 17 and alesser rials indicated' above. The copper tinsel referred to is copperin fine ribbon form such as is commonly used in the flexible conductorscomprising telephone cords and similar types of electrical conductors,which has been gathered into a bundle and matted to cause it to. fit inthe tray 15. It should be understood that the invention may besatisfactorily practiced through the substitution of such othermaterials in each of the respective classes .as will-meettherequirements laid downabove for those classes of materialsi Should thematerial of the first class which quantity of copper tinsel l quantityof magnesium powder 16 as examples of the classes of mateis used becopper tinsel, and should the ma-l terial of the second class which isused be magnesium powder, it is sucient that 25 grams of copper tinseland 10 grams of magnesium powder be used in an annealing containerhaving a capacity of about 15 liters and'designed to receive about 200pounds of material, although the quantities may be ingroove creased ordecreased to accommodate the size bf the container used, A lid 18 havinga de- A pending rim 19 covers the container, tray and contents thedepending rim fitting within a 20 between the inner portions 13 and ythelip groove 22 is filled with a stiff clay-composed of cupola loam 21,the upper surface being troweled flat. A suitable quantity of sealingmixture 22, preferably ofthe' type described in theapplication of B. J.Babbitt, for Annealing seals, Serial No. 316,146, iled October 31,-1928, is sprinkled on the loam around the circumference of the lid. l I

After preparation in the above indicated manner, the container is placedin a furnace (not shown) and heat is applied thereto. Assume that thecustomary maximum tempera-l ture for annealing iron parts is 900 C. Asheat is applied to the container the temperature within is slowly andsteadily increased from the initial room temperature, and a substantialportion' of the oxygen is driven out through the loam seals by heatexpansion of .the air remaining within the container. Being of amaterial and in such form as to be more readily oxidizable at lowertemperature than the iron articles stored in the container,

\ the copper tinsel will absorb a large portion of the oxygen remainingin the container after the temperature has been raised to approximately600 C., and the combination of the copperl tinsel with oxygen willcontinue until a point is reached commensurate with the oxidationpointof the more energetically combustible magnesium. Experiments have shownthat the magnesium combines with oxygen at a point somewhat lower thanthat at which the iron parts -would become materially oxidized. Owing tothe great. 4natural affinity of magnesium, and other metals in itsclass, for oxygen the combination between the oxygen remaining in thecontainer and thev magnesium powder has been found to take place withsuch energy that not only is all trace of oxygen removed from contactwith the iron parts, but themagnesium has been found to act as areducing agent on those portions of the parts which may have previouslybecome oxidized. The remainder of the annealing process is carried onwith the metal parts being heated in an atmosphere entirely free, fromoxygen, no traces of oxidation will remain .upon the surfaces of theparts at the completion of the process and subsequent cooling steps andthe articles will be found to possess the de'- siredA bright anneal.

' By the employment of the above method it may lbe seenv that a verysmall additional amount of labor beyond that which is ordinarilyrequired to load and seal an annealing containervwill be required. Sincecopper tinsel in a form suitable for the practice of this method may beyproduced as a by-product 12 of the vertical side walls. The` of themanufacture of telephone cords and since a comparatively small amountof-magnesium powder is required, it will be observed that the cost ofbright annealing parts is not materially increased in spite of the factthat much better results are procured tainer copper tinsel and acombustible metal ,v

of. the group including magnesium and .alummum in powder form, sealingthe container,

vand applying heat.

3. A method of annealing parts which consists of associating with theparts in a container a quantity of copper tinsel and a lesser quantityof magnesium powder, sealing. the container, and applying heat.

4. A method of annealing parts which consists of associating with theparts in a container copper tinsel'and magnesium powder in theproportions of 2.5 to 1.0 by weight, sealing the container, and applyingheat.

5. A method of annealing parts which consists of associating with theparts in a container of 15 liters capacity 25 grams ofI cop-v per tinseland 10 grams of powdered magnesium, sealing the container,l heat. Y,

6. A method of annealing parts which consists of associating with theparts in a container copper tinsel and an'easily oxidizable metal of thegroup which includes magnesium and aluminum in powder form, sealing thecontainer, and applying heat.-

7 A method of annealing parts which consists in associating with theparts in a container a quantity of copper tinsel and a lesser quantityof powdered aluminum, sealing the container and applying heat.

8. A method of annealmg parts which con- -sists in associating with theparts in a conand applying In witness whereof, I hereunto subscribe myname this 12th dav of October, A. D. 1928.

' ROGER VERDEN WILSON,

